Moving away from the Near-Horizon Attractor of the Extreme Kerr Force-Free Magnetosphere

TL;DR

This paper investigates force-free magnetospheres around extreme Kerr black holes, showing that deviations from the near-horizon attractor lead to magnetically-dominated solutions with finite angular momentum, using second-order perturbation analysis.

Contribution

It demonstrates how moving away from the NHEK attractor yields new magnetically-dominated solutions in extreme Kerr black holes.

Findings

Deviations from the NHEK attractor produce magnetically-dominated solutions.

Second-order perturbation analysis reveals finite angular momentum outflows.

Near-horizon attractor solutions are not unique when moving away from the NHEK limit.

Abstract

We consider force-free magnetospheres around the extreme Kerr black hole. In this case there is no known exact analytic solution to force free electrodynamics which is stationary, axisymmetric and magnetically-dominated. However, any stationary, axisymmetric and regular force-free magnetosphere in extreme Kerr black hole approaches the same attractor solution in the near-horizon extreme Kerr (NHEK) limit with null electromagnetic field. We show that by moving away from the attractor solution in the NHEK region, one finds magnetically-dominated solutions in the extreme Kerr black hole with finite angular momentum outflow. This result is achieved using a perturbative analysis up to the second order.